Hub structure



FIG. 1 is a perspective view of a hub structure in accordance with the invention.

FIG. 2 is a front elevational view of the hub structure of FIG. 1;

FIG. 3 is a left side view of the hub structure of FIG. 1; and,

FIG. 4 is a top elevational view of the hub structure of FIG. 1.

The broken lines are included for the purpose of illustrating environmental structure and form no part of the claimed design. 

The ornamental design for a hub structure, as shown and described. 